[Elecraft] KRX3 roofing filter matching for diversity receive

[Richard Ferch]

W5EWA wrote:

> 	So is the information in the manual just the easy way to set it up,
> and you can actually put them in whatever slots you want?
>>From reading the manual I understood that they had to be in decending order
> starting from FL1, and the filters in both receivers had to match for
> diversity receive.

You should always follow the manual carefully. The manual says that 
filters should be in descending order of width, but they do not have to 
be in consecutive slots.

For example, in my main RX I have a 2.7 kHz in slot 2, a 500 kHz in slot 
4, and a "250 Hz" (configured to switch in at 350 Hz) in slot 5. Slots 1 
and 3 are open. In the sub-RX I have 2.7 kHz and 500 Hz filters. I could 
have installed the sub-RX filters in slots 1 and 2, or 4 and 5, or 1 and 
5, or ..., but I chose to install them in slots 2 and 4 simply to reduce 
confusion.

For diversity receive, you should have similar filters in both 
receivers, e.g. matched pairs at the bandwidths you usually use during 
diversity receive. If the filters are 5-pole filters, the offsets should 
be matched as well. Note that during diversity receive, if the filters 
in each receiver are not identical (as in my case below 350 Hz widths) 
you may hear phase modulation, although in my case I can't say that this 
has ever been a serious problem - to me it sounds rather similar to the 
AFX feature.

There is one other restriction: if you plan to transmit in FM, you must 
have an FM filter in slot 1 on the main board.

73,
Rich VE3KI